1. Field of the Invention:
The invention relates to audiometric testing systems and methods.
2. Description of the Prior Art:
Manufacturing organizations are frequently confronted by problems relating to the harmful effects of industrial noise on hearing of employees. Such companies are subject to liability for hearing damage which can be shown to have been caused by industrial noise levels. Well-being of employees requires that the effects of industrial noise on individual employees be periodically monitored to identify employees who experience hearing threshold shifts. It is further necessary to identify manufacturing areas which produce a sufficiently high noise level to induce hearing threshold shifts in employees. It is also important for manufacturing organizations to be able to provide legally admissible evidence to demonstrate that hearing threshold shifts may have occurred for reasons other than presence of industrial noise.
Various audiometric testing techniques are well known. Some known audiometric testing techniques are described in "Audiometry: Principles and Practices", by Aaron Glorig, M.D., Williams & Wilkons Co., Baltimore, Maryland, 1965. Various threshold bracketing techniques are commonly utilized to determine a person's (hereinafter referred to as a test subject, or simply subject) hearing threshold (hereinafter referred to simply as "threshold" or "threshold level") at various frequencies by incrementing or decrementing the intensity of a test tone applied to one of the subject's ears until he or she satisfactorily indicates that he or she has heard the test tone. A quantity known as the "pure tone average" is commonly computed by averaging the subject's threshold at three frequencies, such as 500, 1,000, and 2,000 cycles per second. Another standard calculation is the percent binaural impairment, which indicates deviation from average or standard hearing levels.
Various audiometers are known, including manual audiometers and automatic audiometers. The most complex prior audiometers automatically produce test tones of varying intensities at various frequencies in response to response signals from the person being tested to bracket the threshold levels of the subject. The state of the art is generally shown by U.S. Pat. Nos. 3,974,335; 3,392,241; 3,808,354; 3,809,811 and 3,810,316. None of the known audiometers operates either as an automatic audiometer or as a manual audiometer, and none of the known audiometers calculates audiometric parameters such as pure tone average and/or percent binaural hearing impairment. Known audiometers do not compare the subject's present test results with his previous test results. In summary, there is a presently unmet need for a low-cost system and method for performing audiometric testing and associated bookkeeping tasks to enable manufacturing employers to economically implement necessary hearing conservation programs.